It appears that I have uncovered another leaf that GRRM took from Tolkien's book, a very subtle leaf that only one learned in the lore of Arda (Tolkien's fantasy universe) would spot amongst GRRM's thorns. And spotting, that it clarity of sight, is the exact nature of this discovery, for their is an unmistakable kinship between the Palantír of The Lord of the Rings and the Glass Candles of A Song of Ice and Fire.
The Palantír were made by the Elves of Valinor in the Undying Lands, the acknowledge apex of civilization in Arda. Called the Seven Seeing Stones, they resembled large dark glass spheres with murky depths (but are in truth indestructible dark crystals) and with them those with the skill and will can gaze upon many things across the face of the world. Gaze and communicate with those looking into other, different, Palantír despite the Seeing Stones being scattered across the vast realms of Gondor and Arnor. These magical artifacts burn with a strange inner fire when used and were rescued from the Downfall of Númenor by Lord Elendil and his sons and taken to Middle-Earth where they were set up in various towers across the Realms in Exile.
As to the Glass Candles, they were made in Old Valyria, the acknowledge apex of civilization in the world of A Song of Ice and Fire (see my comparison of Valinor and Valyria in my GRRM the Anti-Tolkien page). Like the Palantír they are dark, though of twisted and razor-sharp obsidian as opposed to smooth crystal, and it t is claimed that when the glass candles burn the sorcerers can see across mountains, seas and deserts, give humans visions and dreams and the ability to communicate with one another half a world apart. Sound familiar? Well, if not, then I should also say that these Glass Candles were rescued from the Doom of Valyria and give off twisted light when they burn. In GRRM's universe their most noted home is the Citadel, the great tower home and HQ of the Maesters.
Again this is a subtle point, but an unmistakable one, and illustrates well enough that George R.R. Martin may have borrowed more from J.R.R. Tolkien than is commonly believed.